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124 Cards in this Set
- Front
- Back
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Describe the two types of phages.
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1. Virulent (Lytic) - produces progeny viruses and kills the host cell by bursting the cell envelope
2. Temperate - gets integrated into the host cell and the life of the host cell can go on |
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Why can't a virus replicate without a host cell?
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Because the host cell provides proteins, amino acids, nucleotides for the virus
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What are capsomers?
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Structural proteins that spontaneously assemble into the triangular plate by binding to each other -- which will later form the icosahedron structure of the phage
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What is a nucleocapsid?
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Protein that contains genetic info
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Describe TMV
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Tobacco Mosaic Virus - disease caused in tobacco plants whose RNA and proteins were used to replicate.
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Describe the T4 phage structure
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Head - composed of the double-stranded, linear DNA chromosome and the capsomer
Tail - contains the collar, sheath, core, base plate, 6 tail fibers, and spikes (There are different proteins for the spikes, fibers, collar, etc.) |
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How does the T4 phage DNA chromosome enter the host cell?
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The spikes from the tail penetrate through the membrane of the host cell and makes a small hole for the chromosome to inject into, but the host cell must have receptor proteins on the outer membrane that is recognized by the tail fibers of T4.
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How long is the growth of a T4 phage?
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25 minutes
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Describe what happens during the growth of T4 phage?
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0-10 minutes - DNA synthesis: early proteins, DNA polymerase and nucleases chew up most of the chromosomes and transcription factors modify the host RNA polymerase
10-20 minutes - late proteins and mostly structural proteins assemble the progeny, capsomers, tail, and collar 15-23 minutes - host cell gets infected with T4 phage progeny 25 minute - last stage where the lysozyme causes the cell to lyse and burst the cell envelope and release the new progeny |
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List the five stages of growth
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1. Absorption/attachment - controlled by specificity that depends on the receptors
2. Injection/Penetration - of chromosome into the cell where the sheath contracts 3. Replication of components - transcription, translation, energy, precursors, and ribosomes are all provided by the host cell to produce viral mRNA, viral DNA or RNA chromosome, and viral structural proteins 4. Assembly - DNA or RNA is packaged, the tail is added, and the viruses are produced 5. Lysis/Release - lysozyme causes membrane to lyse and burst and peptidoglycan also hydrolysis and the progeny is released |
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What is the formula for burst size?
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Avg # of colonies / Infected cell
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What does the absorbance vs. time graph look like when T4 is introduced into the culture?
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Absorbance increases over time and then decreases since the T4 phage will destroy and lyse the cell membrane
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What is the + strand?
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The + strand has the same sequence as mRNA and acts like it
The + strand will mate with a - strand, and produce all + progeny |
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What are not in phages?
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Ribosomes, energy generating system, and very few enzymes
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List the differences between phages and bacteria
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Size - phages are smaller than bacteria
Nucleic acid content - phage chromosome is either RNA or DNA, but bacteria chromosome is DNA Outer structure - phages have a capsid protein layer and bacteria have cell wall and cytoplasmic membrane Growth - phage growth occurs only in living cells and with direct synthesis of components and assembly, bacteria can grow on cultured media and grow by binary fission |
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Describe the lambda phage
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The lambda phage is a temperate phage with double-stranded circular DNA chromosomes that can do lytic or lysogenic growth. The ends of the lambda phage have cohesive sites that are single stranded and will stick to each other to form a circle
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Define the integrase.
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Integrase allows integration to occur at the prophage attachment site and catalyzes breaking and re-joining of lambda DNA with host DNA. Integrase cuts both DNA at specific sites and crossing over between the strands occur and the lambda DNA gets rejoined to the host DNA to create the lambda prophage
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What happens with X (chi) infects the host cell?
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Absorption and penetration into the cell, then the chromosome circularizes and lytic growth or lysogeny occurs (the chance of either is 50/50 percent)
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What does translation produce?
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Repressors, integrase, and DNA replication
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What do repressors do?
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They will bind with operators and inhibit transcription of genes in lytic growth and stimulates its own transcription
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Describe the competition between repressor and lytic proteins.
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There is competition between the repressor and lytic proteins, but the repressor wins so lytic genes are shut off
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Establishing lysogeny after infection requires?
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C1, C2, C3, INT, and CRO anti-C1 repressor
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C2 stimulates?
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RNA polymerase to transcribe
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Where does CRO bind to?
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CRO binds more tightly to O3 than O1, which leads to competition between the CRO and the repressor at those operators which will turn off early functions and limit transcription
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Describe C1.
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C1 inhibits lytic gene expression and stimulates its own transcription and inhibits all others
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Define Pr, C1, C2, C3, CRO, Prm, and Pre
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Pr - principle promoter that produces mRNA that codes for CRO, C2, and replication proteins
C1 - facilitates lysogeny C2 - activates Pre and P1 C3 - prevents C2 degradation CRO - facilitates growth Prm - maintains lysogeny Pre - establish lysogeny |
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Steps for lambda DNA
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1. Lambda DNA is penetrated, circularized, and the host RNA polymerase transcribes early functions
2. C2 activator stimulates transcription from Pre to P1 and early transcription of C2 transcription factor allows the C1 promoter region and INT promoter region to be transcribed 3. CRO binds Or3 and prevents Prm from functioning and competes with repressor so that lytic growth and lysogeny are 50:50 4. C1 repressor binds and shuts off early genes and turns off Prm |
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Define genetic recombination.
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Genetic recombination is the breaking and joining of DNA chromosomes, molecules, or fragments
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What are the three types of recombination?
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Homologous - any regions of DNA, as long as the nucleotide sequences are identical or very similar
Site specific - two fragments only if they contain specific sites (nucleotide sequences) recognized by a specific enzyme Illegitimate - fragments with no similar sequence; rare; and have errors |
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What are the three ways to transfer DNA?
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Transformation, transduction, and conjugation
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Describe the steps of homologous recombination.
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1. One strand gets nicked and a 3' end is generated on the SS-region, Duplex gets invaded by that SS and the hydrogen bonds that are complementary to the nucleotides combine
2. Nick lowers strand of mutant strand and transfers to the lower duplex and they join together by DNA ligase 3. Nick the remaining parental strands, rotate and exchange the right ends up and down, ligase will join the 5' and 3' ends Summary: parental a_b/A_B, recombination a_B/A_b |
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What does horizontal nicking do?
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Horizontal nicking makes two strands that are like parental and two recombinant chromosomes after replication
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What can wild-type fragment invasion do?
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Single stranded fragments recombine into a chromosome by a wild-type fragment invasion
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List the types of reactions make disease or no disease
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Smooth, glistening capsule + wild-type injection = disease and blood culture is wild-type
Rough, no capsule + mutant = no disease and blood culture is negative No colonies + heat-killed wild-type = no disease and culture is negative No colonies + mix mutant and heat-killed wild-type = disease and blood culture is wild-type |
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Describe the recombination that happens when a mutant cell gets injected with wild-type DNA
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In a rough mutant cell that gets injected with wild-type DNA, it undergoes homologous recombination to produce a degraded fragment that contains some mutant DNA and some wild-type DNA
Replication occurs by binary fission to produce one rough mutant and one wild-type cell but the wild-type cell is expressed |
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How does transformation by a plasmid DNA occur?
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Plasmid gets inserted into a host cell and any bacteria to resistant to the plasmid will be isolated of the plasmid DNA. The cell will break and separate plasmid DNA from chromosome fragments and lead to the preparation of plasmid DNA
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List the steps to generate a single-stranded region with 3' end REC BCD enzyme and Chi site
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1. Helicase, which has ss nuclease activity, will invade the duplex and unwind it so the double strand is unwound and cleaved at the 3' end. The helicase will remain active until it hits the Chi site
2. The presence of the Chi site will stimulate recombination and when the REC BCD enzyme encounters the Chi site, it's specificity changes and the nuclease will start hydrolyzing from the 5' end. 3. The chi site is used to generate the 3' end which loads the REC A protein that coats for single strands and catalyzes homologous pairing and strand exchange |
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Define transduction
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When phages move bacterial genes from one host to another
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Describe the two types of transduction.
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Generalized - any host gene; phages grow on the donor (first host) and some phages that are produced pick up the donor chromosome fragment and the new phages will infect the recipient (second host) and transfer the donor DNA to recipient.
Specialized - only host genes near prophage; can be moved; induction is the start where some of the phages formed are picked up near the donor DNA and the phage lysogenizes the recipient and carries the donor DNA |
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Describe the two steps in generalized transduction
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1. Grow P1 on the donor with wild-type and phage, absorption and penetration occurs to allow the host cell to produce the phage head, tail and P1. Assembly occurs where the P1 chromosome is packaged and head and tail are connected to produce a particle that looks like the phage but not a phage (translucent particle)
2. The recipient is infected with P1 grown on the wild-type. The recipient is a leucine-requiring mutant and the wild-type is not. The wild-type tail absorbs and penetrates the plasm and it enters the cell but the wild-type escapes degradation. Homologous recombination occurs near right and left ends and the mutant removed wild-type is incorporated so that the cell produced is completely wild-type |
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Describe the three steps of specialized transduction.
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1. Lysogen is made by mixing the lambda phage with the wild-type which will lyse some cells and lysogenize other cells. By infecting the host with lambda phage some of the host will be destroyed and some will be lambda prophage
2. Induction of prophage: DNA damage will cleave the repressor and the lytic genes will no longer be inhibited and causes an excision in lytic growth so that lysis occurs and the progeny phages are produced; excisionase catalyzes site specific excision and site specific recombination 3. Mix phage preparation by selecting gal+ transductants and plate them on galactose to act as the sole carbon source. The recipients infected by lambda cannot form colonies unless they're infected by lambda Gal+ |
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How does the lambda transducing particle transduce?
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The linear lambda Gal+ DNA in phage gets injected and circularizes. The small circle gets integrated into a bigger chromosome by butting the BOB' and BOP' to join them together. Integrase will cut the common cord at BOP' and BOB' and the new ends are joined together
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Can Gal+ phenotype and Gal- mutant grow on galactose?
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Gal+ phenotype can use galactose as sole carbon source
Gal- mutant won't grow on galactose as sole carbon source because it can't catalyze one of the reactions. but it can grow on glucose |
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What is the genotype of the mutant with respect to galactose?
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Partial diploid because it contains two copies of the gene in which one is mutant and one is wild-type
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What are mobile genetic elements?
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chromosome pieces that can move from one site in the cell to another site and movement between cells are lateral
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List the general characteristics of a plasmid
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Small
Circular, double-stranded DNA 5-50 genes Cytoplasmic location is not essential for growth normally Needs replication genes and sites in order for plasmids to be replicated 1-2 copies each per cell Several different plasmids per cell |
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What is a resistance factor and resistance transfer factor?
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Resistance factor - contains all regular plasmid characteristics and carry genes which encode proteins which make the bacterial host resistant to antibiotic
Resistance transfer factor - all general plasmid characteristics and the ability to transfer plasmid in mating |
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What are the mechanisms for drug resistance?
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1. Mutation results in altered bacterial protein that still has to be able to perform normal functions but it can no longer recognize the antibiotic
2. Bacteria acquire new gene which codes for an enzyme which destroys the antibiotic 3. Bacteria acquire new gene which codes for an enzyme that will pump antibiotic outside the cell |
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Describe the Insertion Sequences (IS)
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Simplest and move rarely
Short and linear sequence that usually only codes for one gene that can transposes to multiple sites in DNA and no phenotype is presented unless the host gene is disrupted |
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List the general characteristics of transposons.
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5-10KB
Linear Transpose to multiple sites Carries antibiotic resistance genes and transfers drug resistance Many are bracketedby two inverted insertion sequences |
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Describe integrons
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Gene capturing elements that code for information necessary to insert host gene into itself, but requires integrase to move the DNA fragment and an attachment site to put the gene into.
Has a promoter to express captured gene, or the captured fragment could have its own promoter Acquires various host genes and can exist in many forms that differ in number and identify of captured genes |
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How are integrons involved in the mobility of DNA?
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Since integrons are located on transposons and are on conjugation plasmids, when they catalyze movement of host genes into themselves, the overall result is movement of genes into transposons and conjugate plasmids
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Describe conjugative transposons.
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they can move from the donor genome into the recipient genome -- some will move to new sites and some move to identical sites
Requires cell to cell contact 20-100KB with genes for integration from recipient genome and excision from donor genome, conjugation, and antibiotic resistance |
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Describe genomic islands
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Linear double-stranded DNA
10-20,000KB Located in chromosomes Carries genes for integration and transfer enzymes Integrates in 3' ends of tRNA genes which are similar in sequence to prophage attachment sites Boundaries are direct repeating sequences Differ from host chromosomes in G and C content of DNA indicating origination in another genus Permits evolution in quantum leaps |
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List 4 genomic islands and examples.
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Pathogenicity island - vibrio cholerae
Ecological island - phenol catabolism, pseudomonas putidas Symbiosis island - nitrogen fixation, mesornizobium loti Saprophytic island - e.coli growing in intestines |
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What are the four pathogenicity islands?
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PAI-I: codes for hemolysin which makes blood cells lyse and cannot transport O2 and releases iron into the blood
PAI-II: codes for hemolysin and adhesion PAI-III: codes for adhesion and iron uptake PAI-IV: iron uptake |
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Define conjugation.
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Mating between males and females
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What's the difference between the male and female in conugation?
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The male is the donor and has the fertility factor
Female is the recipient and lacks an F factor |
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What happens with F+ is crossed with F-?
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Results in two F+ cells because the conjugation bridge forms between the F+ and F- cell so that the F factor can be duplicated into the F- cell making it an F+ cell
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What is HfR and how do you form one?
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HfR = High frequency recombinant
To form - an F factor is integrated into the chromosome and the F+ becomes HfR |
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What happens with F- is crossed with HfR?
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Products are one HfR and one F-
Originally, HfR is PRO+ and STR-S and F- is PRO- and STR-R When they are crossed the PRO- gets stripped out of a chromosome as PRO+ gets integrated because of recombination. The linear PRO+ fragment is degraded and the recombinant PRO+ which is HfR and STR-R which is F- |
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How can HfR excise the F factor to generate an F+ factor?
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The HfR chromosome is looped out and homologous recombination occurs so the loop is excised to create an F+ male
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What is the F'?
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F factor with a chromosome that occurs from illegitimate recombination because the HfR PRO+ STR-S chromosome is looped out to create PRO+ loop and an STR-S strand
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What happens when F' is crossed with another F'?
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Results in F' and a new F+
One F' will have STR-S and PRO+ and the other will have STR-R and PRO- |
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What is the genotype of the F' that is newly produced from an F' mating?
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The newly formed F' is partially diploid because there's still PRO- with the STR-R and PRO+
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What are the 6 different genetic engineering techniques?
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1. Transformation by plasmids
2. Cutting DNA at specific sequences with restriction enzymes 3. Molecular cloning of foreign DNA into vectors to generate a hybrid DNA molecule nobel 4. Determination of DNA sequence model 5. Synthesis of DNA strands of predetermined sequence 6. PCR which amplifies any specific DNA fragment or gene nobel |
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What do restriction enzymes do?
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The recognize foreign DNA and will cut specific nucleotide sequences of 4-6 base pairs
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What does modification mean?
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A chemical modification of "own" DNA where DNA is synthesized within it's own cell so that it can be cleaved by the restriction enzyme
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An enzyme in extract can...?
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Recognize and cut foreign DNA
Cleave foreign DNA at specific sites with restriction enzymes that are present in DNA within genes or outside genes |
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How do sticky ends occur?
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Sticky ends will occur when the restriction enzymes don't cut the duplex symmetrically
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Describe the steps of molecular cloning.
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1. Construct a hybrid DNA molecule where the target is the gene or DNA fragment of interest and the vector is the plasmid or phage
2. Introduce the hybrid DNA molecules into the host cell which will replicate the hybrid molecule and allow the target gene to be expressed |
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Why do introns cause problems for cloning?
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Causes problems in cloning in humans or any higher organism genes because they are too long
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List the steps for molecular cloning in higher organisms.
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1. Splice out introns and purify the DNA
2. Copy mRNA into DNA with reverse transcriptase and use this DNA as the target 3. Cut the target DNA with restriction enzymes 4. Purify the vector DNA and cut it with restriction enzymes 5. Mix the target DNA and vector DNA and inactivate the restriction enzyme, anneal, and ligate 6. Transform bacterial host cell, select transformants, identify those with hybrid plasmid which will contain the c-DNA clone |
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What are the properties of cloning vectors?
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Should be small, easily isolated molecules, have only one site for restriction enzymes to be used and the restriction enzyme site shoul dbe in some location other than the essential gene. Should carry some selectable gene or marker and must be replicons that are capable of being replicated when host cells grow and divide
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Describe how PCR amplifies specific DNA fragments after the chemical synthesis of DNA is defined.
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The double strand is denatured and are separated so that primers can be added to each strand. Annealing occurs and polymerase will polymerize complementary strands with DNA polymerase to produce new strands
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Between primers, what is the amount of DNA?
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The amount of DNA is doubled
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What is the advantage of sequencing genes?
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It allows us to know all sites and functions of that gene
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Define genomics
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The study of all genes and sites within chromosomes of an organism by determining and analyzing the nucleotide sequence of the entire chromosome
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What are the two types of genomics?
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Functional genomics - study of functions of a cell or organism by analysis of chromosome nucleotide sequence
Structural genomics - study of 3D shapes of proteins by comparison of amino acid sequences to protein structures databases |
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Define homology.
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Extent of similarity or identity between genes or proteins
Proteins with the same function often have similar amino acid sequence Genes with similar proteins have similar nucleotide sequences - proteins/genes that are very similar have high extent of homology Although two proteins are unrelated, the same amino acid could be located in the same spot but they aren't similar or significantly related |
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What is shotgun sequencing?
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Random sequencing of fragments of a whole genome
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In what direction does cloning occur?
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it can occur in either direction with a small volume and automation
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What forms a contiguous region?
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Overlapping regions of nucleotides on more than one strand of clones that were generated from a similar sequence
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Describe the contiguous region in prokaryotes.
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There's only only one stop and one start codon with no introns and has a Shine-Delgarno sequence
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What is the difference between orthologous proteins and paralogous proteins.
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orthologous - similar proteins from different species
paralogous - similar proteins within the same organism paralogs |
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What are DNA arrays/gene arrays/microarrays/DNA chips?
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DNA fragments that correspond to every gene fixed to a tiny separate spot on a slide and are used to detect and quantitate mRNA from every gene
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What are the steps to make an array and hybridize a microarray?
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1. Making the array from extract chromosomal DNA, amplify the fragments by PCR corresponding to each ORF and affix each fragment to a separate spot on the slide
2. Extract the RNA from either aerobic or anaerobic culture and synthesize cDNA from each mRNA by reverse transcriptase 3. Hybridize cDNA to microarray to quantitate cDNA by mixing the aerobic and anaerobic tagged DNA and then anneal it to be able to measure the amount of aerobic and anaerobic - the amount of cDNA reflects the amount of mRNA of each gene |
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What is the core gene pool?
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Chromosomes for each species that has to include replication, transcription, translation, glycolysis, and cell wall
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What is the flexible gene pool?
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Genomic islands, phages, plasmids, integrons, transposons, insertion sequences
Finds genes for pathogenicity, drug resistance, toxicity/secretion, and cojugation |
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What is the classification of animal virology based on?
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Nucleic acid content and shape
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Where can the naked icosahedral of double stranded DNA virus and single stranded DNA virus assemble?
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Double stranded DNA - In the nucleus for smaller cells and cytoplasm for larger ones.
Single stranded DNA - assembles in DNA |
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What are the three types of enveloped double stranded DNA virus and where do they assemble?
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1. Icosahedral - assembles in the nucleus
2. Helical - assembles in the nucleus 3. Complex - assembles in the cytoplasm |
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Where does the double stranded RNA virus assemble?
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Naked - icosahedral: assembles in the nucleus
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What are the two types of strands of the single stranded RNA virus?
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Positive strand - identical to mRNA and can be naked or enveloped and all assembles in the cytoplasm
Negative strand - complementary to mRNA and are all enveloped and helical and assembles in the cytoplasm |
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Which is more complex, naked or enveloped?
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Enveloped is more complex than naked.
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What are receptor proteins used for?
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Absorption of the host cell by the virus requires the host cell to have receptor proteins on the surface so that the virus can attach to the host.
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What is tissue tropism?
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Absorption to only certain tissues within the host cell
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Define fusion.
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When the viral envelope and host cytoplasmic membrane fuse together and the virion is released into the cytoplasm
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Why can't viruses undergo endocytosis-phagocytosis?
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They undergo invagination of the cytoplasmic membrane instead
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What are the steps of DNA synthesis?
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1. Uncoat the cytoplasm and transport the virus into the nucleus in order to circularize the chromosome.
2. Transcription of the chromosome inside the nucleus occurs and then translation in the cytoplasm 3. The viral proteins are transported into the nucleus and replicated by viral DNA polymerase 4. The nucleocapsids are assembled in the nucleus and inserted n the RER and nuclear membrane 5. Budding of the nucleocapsids from nuclear membrane and RER where they acquire an envelope 6. Exocytosis to release the virus |
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What are the early steps of herpesvirus replication?
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1. Attachment of the viral protein to the cellular receptor
2. The envelope is released and the nucleocapsid goes to a nuclear rope 3. Viral DNA enters the nucleus and circularizes 4. Transcription of early genes and mRNA export 5. Immediate-early proteins are transported to the nucleus 6. alpha proteins are involved in beta-mRNA synthesis |
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What are the late events of herpesvirus replication?
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1. beta-proteins replicate DNA by rolling circle
2. beta proteins lead to transcription of late gamma mRNAs for structural proteins 3. Formation of empty capsids 4. Packaging of unit length DNA into capsids 5. Particles exit nucleus and receive envelope 6. Virons exit by exocytosis |
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What are the steps to replicate an enveloped positive strand of RNA virus?
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1. Attachment of virus to receptor proteins and release the chromosome by exocytosis or fusion
2. Translation of genome RNA and replication and synthesis of subgenomic mRNA 3. translation of mRNA and the capsid proteins are modified and budded off for release |
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List the steps of retrovirus replication.
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1. The virus is fused into the host cell and reverse transcriptase is used to make DNA from RNA and that DNA is transported to the nucleus and integrated into cellular DNA
2. The provirus, when activated, will transcribe a positive strand and the RNA will be translated to produce viral proteins 3. The RNA is incorporated into viral capsids as chromosomes and the viral glycoproteins are inserted into the host cytoplasmic membrane and assembled in the cytoplasm to form capsids 4. Budding occurs so that the virus can obtain an envelope and be released |
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What are the three things in which you can grow animal viruses?
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1. Living animals - inject animal or use vaccinia virus
2. Embryonated eggs - inject eggs and embryo 3. tissue/cell culture - collect the healthy tissue and then cut them really small and separate the individual cells by protease to hydrolyze the connective tissue between the cells and transfer the tissue to the petri dish so that it can grow a monolayer |
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What is the cytopathic effect?
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when cells are killed, their morphology changes but they aren't physically destroyed and they won't grow in a normal pattern
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Why do cells in a monolayer stop growing?
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Because they will bump into each other which inhibits growth
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What do transforming viruses do?
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If a virus is said to be transforming, it can be added to the monolayer of cells to allow growth because transforming cells have lost contact inhibition
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What are the 4 types of viral infections?
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Acute infection - is rapid and relatively short that leads to cell death
Latent infection - the virus stops replicating but it stays in your body forever with no symptoms and leads to cell death after penetration to produce a cell that has a virus that presents no harm Chronic infection - slow release of virus produced at low levels and the cells aren't killed Malignant cell - produced by the activism of host proto-oncogene or insertion of oncogene and transformed into malignant cell |
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What are the types of HHV and some examples?
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HHV 1 - fever blisters about waist, mostly around mouth and lips
HHV 2 - genital herpes HHV 3 - chicken pox HHV 4 - epstein-barr virus (infectious mononucleosis) HHV 5 - blindness in immunodeficient people HHV 6 - roseola (high fevered followed by a rash) HHV 8 - sarcoma in immunodeficient people |
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What's the difference between neurotopic and lymphotropic?
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Neurotopic (HHV 1-3) - grow in nerve cells
Lymphotropic (HHV 4-8) - grow in lymphatic cells and WBCs |
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What is an oncogene?
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an altered host gene carried by a virus
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What is a proto-oncogene?
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a normal host gene before picked up by a virus
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If some oncogenes viruses don't carry oncogenes, how do they alter gene expression?
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by integrating their DNA into the normal host gene
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Define tumor.
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A mass of cells growing in an un-regulated way
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What are the two types of tumors?
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Benign - local, non-invasive, and non-destructive
Malignant - invasive, destructive, and able to spread |
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What are the different types of malignant tumor?
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Sarcoma - connective tissue tumor
Lymphoma - lymphocyte tumor Carcinoma - epithelial cell tumor Adenocarcinoma - epithelium tumor Leukema - blood and bone-marrow overproduction |
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Why do transforming cells grow better on tissue culture than normal cells?
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Normal cells won't multiply as much on a tissue culture as transformed cells because transformed cells don't respond to growth limiting signals
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What do changes in genes or gene expression coding for replication and cell cycle control?
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proteins, hormones, hormone receptors, tumor suppressors (wild-type suppressors)
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What leads to unregulated growth of cells?
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Viral integration into host chromosome that puts host gene under control of viral regulatory proteins - alters expression level
Gene amplification because of viral integration - abnormal over-replication of region of chromosome containing virus and oncogene Translocation of wild-type proto-oncogene from its normal chromosome location to another location with result that expression level changes |
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Define subvirus particles.
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infectious agents that are smaller than viruses
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What are the three types of subvirus particles?
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1. Viroids - circular, SS, RNA molecule with hybridized complementary regions
2. Virusoids - small, circular, SS, RNA molecule; produced during replication by host cells only if the host cells are simultaneously infected by another virus and codes for one of few genes 3. Prions - proteinaceous infectious particles = proteins that get into nerve cells and destroy them; abnormally shaped human or animal nerve cell protein due to mutation |
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What does replication of a helper virus produce?
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products which allow virusoid to replicate and grow
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What happens if an animal eats a prion?
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It will intake the infectious protein and their nerve cells are destroyed
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